Gene deletions helping reduce acetic acid production by Saccharomyces cerevisiae during aerated fermentation

Abstract

Our group is interested in reducing ethanol yield during wine fermentation, to counter the growing sugar content in grapes due to climate change, and avoid the negative impact of increasing ethanol content in the wine market. While respiratory metabolism appears as an attractive alternative to pure fermentation, to redirect carbon flux towards sensory neutral products (CO2), both the Crabtree effect of Saccharomyces cerevisiae and the tendency to increased acetic acid production during aeration (as we have previously shown), constitute a hurdle to industrial application of respiration compatible fermentation conditions. However, mechanisms involved in acetic acid production by S. cerevisiae in the presence of oxygen are yet poorly understood. We addressed this topic by deletion of several genes, HXK2, REG1, PDE2, PDC1 (homozygous) and PYK1 (heterozygous) in the wine yeast strain FX0 (Laffort) background. Some of them had been previously related with the Crabtree effect. Our results show that oxygenation helps reducing ethanol content of wines. However, there is little impact of the deletions on this reduction. Interestingly, some of these deletions do results in a reduction in acetate yields during oxygenated fermentation of natural grape must.